From 8467b7507a5675c41d9c57ae5f60ada1f3b6f6d4 Mon Sep 17 00:00:00 2001
From: Jeffrey Stedfast <jestedfa@microsoft.com>
Date: Fri, 3 Sep 2021 23:18:37 -0400
Subject: [PATCH] Improved MimeParser.StepMboxMarker() logic

---
 MimeKit/MimeParser.cs | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/MimeKit/MimeParser.cs b/MimeKit/MimeParser.cs
index 7d054f9a00..d42e9c45db 100644
--- a/MimeKit/MimeParser.cs
+++ b/MimeKit/MimeParser.cs
@@ -709,6 +709,12 @@ unsafe bool StepMboxMarker (byte* inbuf, ref int left)
 				while (*inptr != (byte) '\n')
 					inptr++;
 
+				if (inptr == inend) {
+					// we don't have enough input data
+					left = (int) (inptr - start);
+					return false;
+				}
+
 				var markerLength = (int) (inptr - start);
 
 				if (inptr > start && *(inptr - 1) == (byte) '\r')
@@ -719,12 +725,6 @@ unsafe bool StepMboxMarker (byte* inbuf, ref int left)
 
 				var lineLength = (int) (inptr - start);
 
-				if (inptr >= inend) {
-					// we don't have enough input data
-					left = lineLength;
-					return false;
-				}
-
 				inputIndex += lineLength;
 				prevLineBeginOffset = lineBeginOffset;
 				lineBeginOffset = GetOffset (inputIndex);